The present invention is directed to improvements in the construction of skids to protect the appurtenances which extend from the bottom of a railroad tank car.
In recent years particular attention has been directed to the problem of protecting the downwardly projecting appurtenances, such as bottom outlet valves, of railway tank cars and thereby preventing the loss of lading therefrom in the instance of a derailment. Current Association of American Railroads (AAR) and Department of Transportation (DOT) railway tank car regulations for stub sill cars require that various projections extending below the tank bottom must be protected.
Various valve designs and skid designs and combinations thereof have been proposed to solve this problem. An example of such a design is disclosed in U.S. Pat. No. 4,184,663. The outlet valve assembly disclosed in this patent has a shear plane such that if the valve assembly is impacted the bottom portion of the valve is sheared off while the closure portion remains intact preventing the lading from exiting therefrom. A skid arrangement is provided around the valve assembly to protect the closure portion of the valve assembly by directing impact forces against the bottom of the tank car into the body of the tank car.
The present invention is specifically directed to providing an improved skid arrangement which more uniformly distributes the impact forces into the body portion of the tank car and yet is relatively light in weight and structurally reliable.